Error 25003. Error occurred while initializing fusion

The Microsoft .Net Framework 4.0 Setup may fail without any error message or the setup may crash during the install phase. You can find the below error message in the Setup log file (Microsoft .NET Framework 4 Setup_******_******-MSI_netfx_Core_*.msi.txt) under user temp folder(%temp%):

The above error indicates that the Custom Action (CA_InstallAssemblyDef.3643236F_FC70_11D3_A536_0090278A1BB8) failed to install an assembly in the Global Assembly Cache. After debugging the issue, I found that dummy CRT file msvcr100_clr0400.dll was present on the system. The Microsoft .NET Framework 4.5 carries dummy versions of these CRT files (the files contain no executable code) for various compat reasons.

As per the installer log, the dummy CRT files were already present before the installation took place: